Paper Coffee Filter Sizes Explained: Matching Filters to Your Brewer

Filter sizes use several naming systems that overlap and do not always agree. Match the filter to the shape and size of your brewer, then check it dry before the first brew.

CoffeeGear editorial team · Updated October 25, 2026

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To match a paper coffee filter to your brewer, start with the brewer's shape (cone, fan, flat-bottom basket or Chemex), then its size number or capacity, and buy a filter made for that pairing. A filter that is the right shape but the wrong size will fold over, slip down or leave gaps, and that is when you get overflow and a slow, uneven brew.

The naming is the confusing part, since brands use numbers, cup counts and letters differently. This guide explains the main families, how to read a pack, and how to check the fit before you pour.

The four filter shapes

Most filters fall into a few shapes. Reference sources such as Wikipedia describe them as cone, fan or boat shaped, flat-bottom or basket, and special shapes for particular brewers.

• Cone with a pointed or rounded tip. Used in V60-style drippers. Hario's cone sizes are called 01, 02 and 03, and a V60 uses a 60 degree cone with ribs and a large drain hole.
• Fan or wedge shape. Associated with Melitta-style drippers. Melitta's "1x" series (1x2, 1x4, 1x6 and so on) is described as sharing the same bottom width and angle and differing mainly in height.
• Flat-bottom or basket. Used in many automatic drip machines and in some pour-over drippers. Basket filters come in sizes that match the brew basket.
• Chemex filters. Square, circle or half-moon sheets made for that brewer, and folded to fit.

Some brewers use their own small round disks, such as the AeroPress. Those are not interchangeable with any of the filters above.

Reading the numbers on a pack

Numbers mean different things in different systems. Wikipedia notes that common US "#" sizes such as #1, #2, #4 and #6 are similar to Melitta's 101, 102, 1x4 and 1x6, but warns that #1 should not be confused with Melitta's round "1" disks and that #2 is not the same as 1x2. That is a good reminder to read the pack, not guess from the number.

Cup counts are a rough guide at best, since a "cup" in coffee equipment is often smaller than a mug. Use the brewer's own size name where one exists, and do not rely on the number of cups on a filter pack.

What the Chemex maker says

Chemex's own FAQ is useful because it spells out the shapes for its brewers. It says half-moon filters (the FP-2 and FP-2N codes) are for the 3 cup and the Funnex, and describes them as shaped to fit the 15 ounce brewers. It also offers pre-folded circles and squares, a plain unfolded circle for people who prefer to fold their own, and says the half-moon filters are not pre-folded because of their size and design.

The same FAQ describes its white and brown filters as working the same way, with the choice a matter of preference. The codes differ for bleached and unbleached versions, so check the code, not only the colour, when you reorder. For a full comparison of the brewer itself, see our V60, Kalita Wave and Chemex guide.

Mismatches and what they cause

The right filter sits flush against the walls of the dripper, reaches near the rim and does not fold over itself. When that does not happen, a few problems show up.

• A filter that is too big. It rises above the rim or folds over, and a folded edge can collapse into the grounds or let water run down the outside. If water flows over the top, it can reach the carafe without passing through the coffee.
• A filter that is too small. It can slide into the cone, pull away from the walls or fold in on itself, leaving gaps where water can bypass the coffee.
• The wrong shape. A basket filter in a cone dripper, or the reverse, rarely sits correctly. You get a collapsed filter or loose edges.
• Slow draw-down. A filter pressed flat against ribs or vents may drain more slowly than one that stands away from the wall. Grind size and pouring technique matter too, so do not blame the filter alone.

If a brew overflows or drains very slowly, check the fit first, then your grind, before you change anything else. Our V60 guide shows how a well-seated filter should look, and the brewer comparison explains how different drippers handle the same coffee.

A dry-fit test before the first brew

1. Open the filter and place it dry in the brewer.
2. Check that it reaches near the rim but does not fold over or stick out.
3. Look for gaps between the filter and the wall. If there are large ones, the size or shape is off.
4. Rinse the filter with hot water, as many recipes suggest, then check the fit again. A wet filter can slump if it was marginal.
5. Keep a note of the exact name and size on the pack that fit, so you can reorder the same one.

For machine baskets, the manual or the maker's parts page tells you the filter shape and size, and our automatic drip guide explains what to check on those brewers. If you are building a pour-over kit from scratch, the pour-over setups guide lists what goes with what.

Bleached, unbleached and other choices

Filters come in white and brown versions, and some makers use different product codes for them. Chemex says the choice is a matter of preference. Whichever you choose, the size and shape are the part that must match, and a rinse before brewing is a common step. This article does not make taste or health claims about either colour.

Frequently asked questions